Rubidium (Rb), chemical element of Group 1 (Ia) in the periodic table, the alkali metal group. Rubidium is the second most reactive metal and is very soft, with a silvery-white lustre. Rubidium and cesium often occur together in nature. Rubidium, however, is more widely scattered and seldom forms a natural mineral; it is found only as an impurity in other minerals, ranging in content up to 5 percent in such minerals as lepidolite, pollucite, and carnallite. Continue reading from Encyclopedia Britannica
Lepidolite was discovered in the 1760s and it behaved oddly. When thrown on to glowing coals it frothed and then hardened like glass. Analysis showed it to contain lithium and potassium, but it held a secret: Rubidium.
In 1861, Robert Bunsen and Gustav Kirchhoff, of the University of Heidelberg, dissolved the ore in acid and then precipitated the potassium it contained which carried down another heavier alkali metal. By carefully washing this precipitate with boiling water they removed the more soluble potassium component and then confirmed that they really had a new element by examining the atomic spectrum of what remained. This showed two intense ruby red lines never seen before, indicating a new element, which they named after this colour. Continue reading from Royal Society of Chemistry
Rubidium is the 25th most abundant element found on Earth. Rubidium forms alloys with other alkali metals as well as with elements such as mercury (known as amalgams) and gold. Rubidium ignites spontaneously when exposed to air and reacts violently with water, releasing hydrogen, which immediately bursts into flames. According to Encyclopedia Britannica, rubidium must be kept in mineral oil or in an inert gas atmosphere. Although a second is defined by the oscillations of a cesium atom, often times rubidium is used in atomic clocks, according to Periodic Table, due to a less expensive price tag. Continue reading from Live Science
